Linux/GTK: add support for gamepad touchpad -> touch screen input

[thesourcehim]

For this I had to somewhat rework SDL input handling and add game controller api usage: if joystick is recognized as a game controller by SDL I open it as a game controller, otherwise fallback to generic joystick open. This is required to receive touchpad events. Additionally I have to filter out joystick events if joystick is open as game controller, otherwise there will be double events.

Touchpad finger coords are translated into touchscreen coords thus making touchpad act like touchscreen. This may be what is wanted in #897, but I implemented it only for Linux GTK frontends. Cli frontend must process changes in touchpad_status structure for touchpad translation to work (just like it does for mouse_status structure).

Note that hidraw access permissions are required to use touchpad, i.e. /dev/hidraw* file corresponding to gamepad must be accessible for user.

[rofl0r]

on first glance doesnt look bad. can the person that filed the original issue do a test and confirm whether it works ? i dont have the required hw to test.

[rofl0r]

apparently the guy cant test it. do you have a touchpad device that you tested it with?

[thesourcehim]

I tested with ps5 dualsense touchpad. Also I'm currently trying to build gtk3 frontend for windows, all dependencies seem to be available via vcpkg, so maybe I'll be able to provide executable for him to test.

Update: I give up trying to build for windows - too many problems with that.